Leaves are browning on edges and curling upward? Pics inside

I need to act fast before it continues. Any suggestions? Third pic is the worst leaf on the plany

 

I havent fed them yet but Im pretty sire the previous owner fed em one every three days. he had em under black lights and no light 12/12 in his closet with no fan. I have no lights and put them in the window but yesterday I had them in direct sunlight for the first time in a while for the plant im guessing.